Perfluoronated cycle-containing tertiary amines used as a basis for gas-conveying emulsions and device for the production thereof

ABSTRACT

Tertiary perfluorocycloamines (TPFCAs) of general formula (1) 
                 
 
where n=1 or 2, m=2 or 3, X is 
                 
 
wherein at n=2 X is 
                 
 
as the basis for gas transport emulsions.
 
     TPFCAs comprise a group of compounds which are close in their physicochemical properties to perfluoro-N-(4-methylcyclohexyl)-piperidine, particularly in the critical temperature of dissolution in hexane, and which are used in a mixture, forming a number of compounds with gradually varying characteristics. Owing to this, a greater homogeneity of the fluorocarbon phase is achievable in the emulsions and it becomes possible to enhance the stability of the emulsion particles stabilized by an ethylene oxide-propylene oxide block copolymer, with the absence of toxicity for large animals. A mixture of TPFCAs is prepared by electrochemical fluorination of n-piperidinoheptafluorotoluene in anhydrous hydrogen fluoride. The use of this mixture of TPFCAs instead of individual perfluoro-N-(4-methylcyclohexyl) piperidine simplifies, speeds up the process for preparing perfluorinated organic compounds, makes it cheaper, and provides conditions for broader application of gas transport emulsions based thereon.

FIELD OF THE ART

The present invention relates to the chemistry of fluororganic compoundsand more particularly to a group of new tertiary perfluorocycloamines(TPFCA). The invention may be used most effectively as a basis forproducing gas transport media intended for the preservation of organs,blood substitution and treating pathologies associated with regionalblood flow disturbances.

STATE OF THE ART

Known in the art is a tertiary perfluorocycloamine,perfluoro-N-(4-methylcyclohexyl)-piperidine, which has the formula

possesses lipophobic properties and is used as a basis for gas transportmedia both singly and in combination with lipophilic perfluororganiccompounds (PFOCs), for instance, with perfluorodecalin (PFD) [see S. I.Vorobyev, G. R. Ivanitskij, K. N. Makarov, V. V. Moroz, V. P.Kutyshenko//Perfluorocarbon Emulsions Stabilized with Nonionogenic BlockCopolymers//in: Collection of Papers “Perfluorocarbon Active Media forMedicine and Biology (New Aspects of Research)”, Pushchino, 1993, pp.33-46 (in Russian)].

In the specification to RU 2088217 published in the Bulletin“Izobreteniya . . . (Zayavki . . . ,)” No. 24, 27.08.1998 it is shownthat introducing a lipophilic TPFCAperfluoro-N-(4-methylcyclohexyl)-piperidine into the formulation of thelipophilic fluorocarbon phase provides the elimination of toxicity inemulsions for large animals, this toxicity being typical of gastransport emulsions containing lipophilic rapidly eliminable PFOCs.However, in spite of all positive properties of emulsions prepared onthe basis of lipophilic PFOCs and lipophobicperfluoro-N-(4-methylcyclohexyl)-piperidine, particles of such anemulsion are insufficiently stable. Their instability under freezing andthawing conditions during storage and when getting into the blood flowis caused, according to calculations and model experiments [G. R.Ivanitskij, S. I. Vorobyev, A. A. Deev//“Life” of PerfluorocarbonEmulsion//in: Collection of Papers “Physiological Activity ofFluorine-Containing Compounds (Experiments and Clinical Tests)”,Pushchino, 1995, pp. 5-32 (in Russian)], by that PFOCs sharply differingin the lipophilicity, particularly in the temperature of criticaldissolution in hexane, form heterogeneous clustered structures in thefluorocarbon phase, that are characterized by permanent turbulent motionwithin the emulsion particles, the stability of the adsorption layer ofthe surface active component being thus disturbed.

Besides, the preparation of perfluoro-N-(4-methylcyclohexyl)-piperidineis a highly labor-consuming and therefore costly process, so that usingthis compound individually involves difficulties. These factors takentogether impose essential limitations on the commercial preparation ofthis compound an on a wide use of gas transport media for biomedicalpurposes.

ESSENCE OF THE INVENTION

It is an object of the present invention to provide new tertiaryperfluorocycloamines close in their physicochemical and biologicalproperties to perfluoro-N-(4-methylcyclohexyl)-piperidine, non-toxic forlarge animals, and improving the stability of emulsions under freezingand thawing conditions and upon getting into the blood flow,

Another object of the invention is to simplify and speed-up thetechnological process of preparing TPFCAs suitable for use as a basisfor the production of gas transport media and displaying an improvedcomplex of useful properties.

Said objects are accomplished by using as the basis for gas transportemulsions a group of tertiary perfluorocycloamines of general formula(1)

where n=1 or 2, m=2 or 3, X is

wherein at n=2 X is

Said group of compounds is prepared by the electrochemical fluorinationof n-piperidinoheptafluorotoluene. This group contains compounds havingclose physicochemical properties which provide their successful use in amixture:

-   two isomers of perfluoromethylpropyl(methylcyclopentyl)-amine,-   cis/trans-perfluoromethylpropyl(methylcyclohexyl)amine,-   perfluoromethylbutyl-(4-methylcyclohexyl)amine,-   cis/trans-perfluoro-N-(4-methylcyclohexyl)-2-methylpyrrolidine,-   cis/trans-perfluoro-N-(4-methylcyclohexyl)-piperidine.

The critical parameter decisive for the possibility of using theproducts of the electrochemical fluorination ofn-piperidinoheptafluorotoluene is the absence of underfluorinatedproducts: hydrogen-containing or unsaturated compounds responsible fortoxicity. In terms of toxicity parameters, the individualperfluoro-N-(4-methylcyclohexyl)-piperidine and a mixture of TPFCAspractically coincide both in the form of liquids and in the formulationof emulsions (Tables 1, 2).

All compounds of this group of TPFCAs are close in thelipophilic-lipophobic properties and in the critical temperature ofdissolution in hexane (CTDH in the range of 34-30° C. with dissolutionof 25 mol. %). In a mixture they form a number of compounds withgradually varying characteristics. Owing to this, a greater homogeneityof the fluorocarbon phase is achievable both in emulsions based on thisgroup of compounds only and on a combination thereof with lipophilicperfluororganic compounds. Thereby it becomes possible to enhance thestability of the adsorption layer of the emulsion particles stabilizedby an ethylene oxide-propylene oxide block copolymer (Table 3). Theemulsions based on the TPFCA group, similarly to the emulsionscontaining individual perfluoro-N-(4-methylcyclohexyl)-piperidine, arenot toxic for large animals (Table 2). In addition, these emulsionsdisplay a better complex of properties manifested in a greater stabilityof the prepared emulsions (Table 3). All this makes these emulsionssuitable for use as perfusion media and blood-substituting compositions.

The electrochemical fluorination is carried out in an electrolytic cellcharged with an electrolyte containing 10-25% of the startingn-piperidinoheptafluorotoluene in anhydrous hydrogen fluoride. Thetemperature is maintained in the range of 20-25° C. The current densityis varied from 200 to 400 A/m² at 5-6 V. The process is run for 10-12hours with periodic replenishing the reaction mixture with a moreconcentrated solution of the starting substance in anhydrous hydrogenfluoride. Depending on the reaction conditions, the yield of thefluorination products is from 61 to 78% of the starting product. Afterthe removal of underfluorinated (hydrogen-containing and unsaturated)products a number of tertiary perfluorocycloamines are obtained with aboiling point within 179-196° C.

All the compounds are identified by chromatographic mass spectrometryand NMR spectrometry techniques. The main compound of the group ofinterest is cis/trans-perfluoro-N-(4-methylcyclohexyl)-piperidine (withthe yield of 60% to 70%). Other TPFCAs are products of partialdegradation and isomerization of the starting substance in the course ofthe electrochemical fluorination. Variations in the percentage ofcompounds in the TPFCA mixture upon variations of thecis/trans-perfluoro-N-(4-methylcyclohexyl)-piperidine content within therange of 60% to 70% do not tell in any substantial manner on thephysicochemical and biological parameters of the obtained emulsions. Atypical chromatogram of the prepared tertiary perfluorocycloamines isshown in FIG. 1 (capillary column, squalane, 100 m).

The described process for the preparation of TPFCA is much simpler andcheaper then the preparation of individual pureperfluoro-N-(4-methylcyclohexyl)-piperidine, whatever process for thepreparation of the latter is used, because the above-described processdoes not require carrying out such labor-consuming procedures aspreparative chromatography and rectification. The process for thepreparation of individual perfluoro-N-(4-methylcyclohexyl)-piperidine isnot described in the literature. Nevertheless, according to ourestimates, the elimination from the process of the preparativechromatography and rectification operations, inevitable in isolating theindividual products, makes the process several-fold simpler, faster andcheaper.

Said TPFCA mixture is used instead of individualperfluoro-N-(4-methylcyclohexyl)-piperidine for the preparation of gastransport emulsions. The simplified technology of the process makes itpossible to contract expenses for the production of TPFCAs and therebyto reduce the production costs of gas transport media with asimultaneous enhancement of the stability and rheological properties ofthese media. All this opens up prospects for the commercial productionand broader use of emulsions of perfluororganic compounds in researchand clinical practice.

The present invention will be further illustrated by an example ofpreparing particular TPFCAs, this example being intended only forsupporting the possibility of carrying out the invention, but not forlimiting the Applicant's claims reflected in the set of claimshereinbelow.

BRIEF DESCRIPTION OF FIG. 1

FIG. 1 is a chromatogram of the prepared mixture of tertiaryperfluorocycloamines (capillary column, squalane, 100 m), which showsthe temperature shift amplitude determined with the help of acatharometric sensor vs. the substance yield time:

peak 1. two isomers of perfluoromethylpropyl(methylcyclo-pentyl)amine,

peak 2. cis/trans-perfluoromethylpropyl(methylcyclohexyl)amine,

peak 3. perfluoromethylbutyl-(4-methylcyclohexyl)amine,

peak 4. cis/trans-perfluoro-N-(4-methylcyclohexyl)-2-methylpyrrolidine,

peak 5. cis/trans-perfluoro-N-(4-methylcyclohexyl)-piperidine.

EXAMPLE 1

Preparation of Tertiary Perfluorocycloamines (TPFCAs)

A 2-liter electrolytic cell with external circulation of theelectrolyte, provided with nickel electrodes having an area of 3000 cm²,was charged with 1500 ml of an electrolyte containing 10% ofn-piperidinoheptafluorotoluene in anhydrous hydrogen fluoride. Theprocess of electrochemical fluorination was carried out at thetemperature of 22° C., initial current density of 200 A/m² and voltageof 5 V. An electrolyte containing 60% solution ofn-piperidinohepta-fluorotoluene in anhydrous hydrogen fluoride was addedperiodically. During 10 hours of the fluorination the current densitywas increased gradually to 400 A/m² by increasing the voltage to 6 V.The total amount of the current passed was 800 Ah, and 330 g ofn-piperidino-heptafluorotoluene were introduced into the reaction.Liquid products of the fluorination were separated from the electrolyte,washed with water, and with sodium bicarbonate solution to remove HF.After removing underfluorinated admixtures, the mixture of fluorinationproducts was distilled, and 388 g (61%) of completely fluorinatedcompounds having a boiling point within 179-196° C. were obtained.According to the NMR spectroscopy and mass spectrometry data, theobtained completely fluorinated tertiary cycloamines comprise five kindsof compounds: 1—isomers of perfluoromethylpropyl(methylcyclopentyl)amine(1%), 2—cis/trans-perfluoromethylpropyl(methylcyclohexyl)-amine,3—perfluoromethylbutyl-(4-methylcyclo-hexyl)amine (2%),4—cis/trans-perfluoro-N-(4-methylcyclo-hexyl)-2-methylpyrrolidine (25%),5—cis/trans-perfluoro-N-(4-methylcyclohexyl)-piperidine (64%) (see thechromatogram in FIG. 1).

EXAMPLE 2

The Use of TPFCA

The completely fluorinated products obtained as described in Example 1were used for preparing a submicron emulsion containing 10 vol. % ofTPFCA, 3 wt. % of an ethylene oxide-propylene oxide block copolymer andan aqueous solution of salts isotonic to blood plasma (120 mM of MaCl,10 Mm of NaHCO₃, 2 mM of KH₂PO₄, 5 mM of KCl, 2 mM of CaCl₂), with 10 mMof glucose, 1 mM of sodium succinate, 1 mM of sodium pyruvate, 1 mM ofsodium 2-hydroxybutyrate (perfusate pH 7.40). With the help of theproduced emulsion, an isolated dog kidney was perfused underrecirculation normothermal conditions (1 liter of the perfusate per 40 gof the kidney). The vital activity of the organ was maintained for 24hours, replacing the perfusion composition every 6 hours, without damageto cell membranes (without edema, without substantial growth of thecapillary resistance, with the perfusate pH being preserved, and withouta drop of the oxygen consumption rate).

EXAMPLE 3

The Use of TPFCA

A mixture of the TPFCAs prepared as described in Example 1 withperfluorodecalin in a 1:2 ratio was used for preparing a submicronemulsion containing 10 vol. % of a fluorocarbon phase, 4 wt. % of anethylene oxide-propylene oxide block copolymer, and an aqueous solutionof salts isotonic to blood plasma (120 mM of NaCl, 8 mM of NaHCO₃, 1.2mM of KH₂PO₄, 5 mM KCl), with 10 mM of glucose. The obtained emulsionwas used for isovolumetric substitution of 65% of the volume ofcirculating blood in 10 rats under general anesthesia withpremedication, with oxygen-enriched air being supplied to the animalsfor breathing in the course of the operation and during the first 24hours after the blood substitution. All the animals which have undergoneblood substitution, survived.

EXAMPLE 4

The Use of TPFCA

TPFCA in a mixture with perfluorodecalin were used for the preparationof a submicron emulsion as described in Example 3. The prepared emulsionwas administered intravenously to ten 2.5-3.5 kg bodyweight rabbits in adosage of 20 ml per kg. The deviation of the body temperature in therabbits after the administration of the emulsion did not exceed 0.3° C.No symptoms of allergic reactions were observed. The content ofleukocytes in the peripheral blood lowered by not more than 5% of theinitial one, this being also indicative of the preparation being notreactogenic. All the rabbits successfully survived the critical periodof 80 days (the period during which all the rabbits die, if an emulsionof pure perfluorodecalin is administered to them). No pathologicalabnormalities were found in the animals throughout the follow-up period(of more than 1 year).

TABLE 1 Comparison of the toxicity* of individual perfluoro-N-(4-methylcyclohexyl)-piperidine (PFMCP) and of a mixture of tertiaryperfluorocycloamines (TPFCAs), and of emulsions based thereon Kind ofPercentage investigated Culture Concentration gain in cell preparationmedium/IP of fluorine growth after (IP) ratio ions (10⁻⁶ M) cultivationCulture medium — 1.0 100% Mixture of PFD 20:1 1.0 90 ± 15% andindividual PFMCP Mixture of PFD 20:1 1.0 90 ± 17% and TPFCA Emulsionbased 10:1 5.5 65-95% on individual PFMCP Emulsion based 10:1 5.5 65-95%on TPFCA *Toxicity of perfluororganic compounds was assessed by theinhibition of the growth of cultivatd transformed lymphoid Raji linecells.

TABLE 2 Comparison of the toxicity of different PFOC emulsions in termsof the half-lethal dose for mice and of the survival of rabbits Survivalof rabbits (in %) one year af- ter the intravenous administration of theinvestigated Kind of Acute toxicity for preparations in investigatedmice, LD₅₀, in ml dosage of 20 ml per preparation per kg kg bodyweightEmulsion based on 140 100.0 individual PFMCP Emulsion based on 150 0.0individual PFD Emulsion based on 140 100.0 PFD and individual PFMCP (2:1ratio) Emulsion based on 140 100.0 PFD and TPFCA (2:1 ratio)

TABLE 3 Comparison of the stability of PFD/PFMCP- and PFD/TPFCA- basedemulsion Enlargement of the Optical density after Kind of mean particlesize mixing the emulsion perfluoror- with the initial size withdifferent concen- ganic com- thereof of 0.08 μm trations of dextran inpounds en- After 5- the 1:1 ratio tering into After 45 fold With- theformu- days of freezing out 3% 6% lation of storage at and thaw- dex-dex- dex- emulsions 4° C. ing tran tran tran PFD and 0.14 ± 0.01 0.15 ±0.02 0.10 0.35 0.88 PFMCP in 2:1 ratio PFD and 0.12 ± 0.01 0.11 ± 0.010.10 0.19 0.62 TPFCA in 2:1 ratio

1. Tertiary perfluorocycloamines of general formula (1)

where n=1 or 2, m=2 or 3, X is

wherein at n=2 as the basis for gas transport emulsions.
 2. Tertiaryperfluorocycloamines according to claim 1, selected from two isomers ofperfluoromethylpropyl-(methylcyclo-pentyl)amine;cis/trans-perfluoromethylpropyl(4-methylcyclo-hexyl)amine;perfluoromethylbutyl-(4-methylcyclohexyl)amine;cis/trans-perfluoro-N-(4-methylcyclohexyl)-2-methylpyrrolidine;cis/trans-perfluoro-N-(4-methylhexyl)-piperidine, displaying closephysicochemical properties and used in a mixture.
 3. A process for thepreparation of tertiary perfluorocycloamines of general formula (1)

where n=1 or 2, m=2 or 3, X is

wherein at n=2 comprising electrochemical fluorination of a startingproduct in anhydrous hydrogen fluoride, characterized in that saidstarting product subjected to the electrochemical fluorination isn-piperidinoheptafluorotoluene.